Lead author Dr Bryan Fry of the University of Melbourne, says their study suggests Megalania (Varanus prisca), which roamed Australia during the Pleistocene, could have weighed at least 500 kilograms and measured 5.5 metres long.

He says using a combined arsenal of deadly serrated teeth and anti-coagulant and hypotension-inducing venoms, the prehistoric lizard could have killed prey as large as a baby diprotodon.

Fry says the study answers confusion over whether the Megafauna lizard was primarily a scavenger or predator.

The assertions are based on an analysis of the cranial mechanics of the komodo dragon, the world's largest extant lizard.

Living relative

Co-author Dr Stephen Wroe, of the University of New South Wales, says when compared with a saltwater crocodile the komodo dragon has a very weak bite.

However, Wroe says the skull is a critical part of the komodo dragon's killing arsenal.

The researchers have found the lizard bites its prey, then inflicts large amounts of damage with its serrated teeth by pulling back.

At the same time it injects venom that prevents blood clotting and rapidly lowers blood pressure.

"What is surprising and impressive is that it manages to inflict a great deal of damage with a very lightweight, gracile skull," says Wroe.

He says the skull is mostly empty space with a series of struts and beam as its framework that is adapted to save weight and allow the lizard more mobility.

"It all comes together as an armoury with a surprisingly sophisticated and complex tool kit," says Wroe.

"It doesn't have a powerful bite, but it is well adapted to bite and pull at the same time.

"And together with very sharp serrated teeth that is enough to open serious wounds in large prey.

"The affect of that is then amplified by the anticoagulant and hypertension toxins it is bathing the wounds in."